Suicide is a leading cause of death in the United States and worldwide. Suicide represents an important, yet preventable public health problem. In 1999, the Surgeon General released a Call to Action to Prevent Suicide. Efforts have increasingly focused on suicide prevention strategies, as well as increased investigations of risk factors for suicidality. A growing area of research includes the study of sleep disturbances and suicide. Changes in sleep are among the top 10 warning signs of acute suicidal risk. Several investigations have found that sleep complaints, such as insomnia, nightmares, and poor self-reported sleep-quality predict increased suicidality. Many of these investigations have failed, however, to examine the association above and beyond the influence of depression. In addition to this, a paucity of research has investigated sleep among more severe suicidal behaviors, such as suicide attempts or completed suicide. Moreover, few studies have investigated the connection between sleep and suicide using objective measurements of sleep. Three proposed studies will examine sleep disturbances as a unique suicide risk factor. Using a longitudinal, population-based sample, the first study will examine the association between poor self-reported sleep quality and risk for completed suicide. The second study will investigate sleep disturbances according to suicidal risk parameters, including suicidal symptom structure and a past history of suicide attempts. The third study will examine the connection between sleep and suicidal ideation using an objective assessment of sleep and a prospective study design. [unreadable] [unreadable] [unreadable]